1. Field of the Invention
The present invention relates to web processing systems, which may perform operations such as forming an image on a web (e.g. of paper) by printing, copying or other marking process, (hereinafter generally referred to as "printing") and/or handling arrangements such as folding or format adjustment. The present invention is particularly, but not exclusively, concerned with processing systems in which the paper or other material orginates as a continuous web on a roll.
2. Summary of the Prior Art
It is very well known to pass paper from a roll through a printing machine to form a series of images on it and then rewind, sheet or fold it into various formats. However, there are fundamental problems which provide a serious limitation to the efficiency of such machines. There is the problem of "down-time". Once the printing machine has been set up, and the paper put in motion, printing can occur very rapidly. However, with the known machines long delays can occur when any change is made to the method of delivery or to what is being printed. For example, if a different image is to be printed, or if the repeat length of the image is to be changed, or if a different colour is to be used, or the folded format is to be changed, then the print run has to be stopped. The design of the known printing machines is such that it is extremely difficult to make such changes, and hence it is common for the time such machines are not working (the down-time) to be much longer than the effective working time.
A further problem of existing arrangements is that printing machines are designed for a specific printing application, the machine being available as a single entity. What this means, in practice, is that if the owner of the machine wants to carry out more complex operations than are currently possible on his machine, he must undertake quite major engineering or buy a whole new machine.